What do you mean by "interactive mode"?
There are "Run" and "Debug" buttons above the source code editor where you can run your code or debug it (do you call debugging "interactive mode"?).
If you mean "interactive mode" to be where the user can enter or read text, then it is the console, just below the source code window, typically a window with a black background. Mind that this window is only available while your code is running.